Meeting Abstract
P1.48 Monday, Jan. 4 Dietary resource partitioning between sympatrically breeding Steller sea lions (Eumetopias jubatus) and northern fur seals (Callorhinus ursinus) on Lovushki Island, Russia. WAITE, J N*; BURKANOV, V N; ANDREWS, R D; Univ. of Alaska, Fairbanks / Alaska SeaLife Center; NMML / Pac. Inst. of Geog., Kamchatka Branch ; Univ. of Alaska, Fairbanks / Alaska SeaLife Center jnwaite@gmail.com
Steller sea lions (SSL, Eumetopias jubatus) and northern fur seals (NFS, Callorhinus ursinus) breed sympatrically on Lovushki Island, Russia. A large population of non-breeding juvenile NFS is also present during the breeding season. After experiencing a dramatic population decline over most of their range in the last 4 decades, the SSL population on Lovushki Island has begun to increase slowly in recent years. Simultaneously, the NFS population has been increasing at a rapid pace, creating the potential for intra-and inter-specific foraging competition. The dietary resource partitioning between these three groups was examined through the analysis of undigested prey remains recovered from scats and spews collected on the rookery. The prey selection of breeding SSL and breeding NFS suggests a partitioning of dietary resources based both on prey selection and spatial foraging location. There was a significant dietary overlap between breeding SSL and non-breeding NFS (Pianka’s niche overlap index Oij = 0.939) but not between breeding SSL and breeding NFS (Oij = 0.231). SSL and juvenile NFS fed primarily on Atka mackerel (Pleurogrammus monopterygius) and walleye pollock (Theragra chalcogramma). Both of these species are low- to moderate-energy prey items that inhabit shallow, near-shore waters. Adult female NFS fed primarily on higher-energy northern smoothtongue (Leuroglossus schmidti) and cephalopods, both of which occur offshore in pelagic waters. While the dietary overlap between breeding SSL and non-breeding NFS is high, without knowledge of foraging locations and times, a high level of competition for prey resources cannot be inferred.
